Women are more likely than men to develop Alzheimer's disease (AD), and available research suggests this is not only because they have a longer life expectancy than men. This increased risk is likely due, in part, to fluctuating sex hormones across the lifespan. Sex hormones likely have direct actions on AD brain biomarkers (A? and tau levels), as well as indirect actions via inflammation, sleep disruptions, and reduced brain blood flow and volume, all of which are independent risk factors for AD. African Americans ?men and women? are also at increased risk for AD vs. Caucasians. As such, mechanistic studies and interventions need to be thoroughly examined and tested in both African American and Caucasian participants. The purpose of the proposed project is to determine the relationship between brain and systemic sex hormones on known AD biomarkers in individuals most at risk for AD. 150 middle age, African American (n=75) and Caucasian (n=75) women will be enrolled in this observational, two year study. The main objectives are to test whether brain and serum sex hormones (estradiol, estrone, progesterone, testosterone) differentially influence AD risk factors (inflammation, sleep and cerebral blood flow,), and if sex hormone levels moderate the relationship between these risk factors and AD biomarkers (cognition, CSF, neuro-imaging). We will leverage existing NIH funded, well characterized cohorts (n=291; followed by MPIs Wharton & Hu), including middle- age women at high risk for AD (through family history or APOE e4 allele) who already have baseline and longitudinal blood, CSF, and MRI analysis for at least 2 years. We will also test our hypotheses in a unique cohort enriched for African Americans based on our extensive track record in recruiting and analyzing aging and AD biomarkers in a diverse cohort. Participants will complete 3 study visits annually. At each year, we will collect medical and medication history, subjective sleep, cognitive testing and questionnaires (stress, sleep, exercise, nutrition) Participants also undergo blood draw for sex hormone and inflammatory markers. At Baseline and Year 2, participants will undergo the aforementioned protocol, AND take part in: lumbar puncture for spinal fluid collection, neuroimaging and will take home a non-invasive monitor for collection of objective sleep data to wear for 1 night. We have assembled a multidisciplinary team with complementary expertise in sex hormones and aging, AD biomarkers, inflammation, neuroimaging, sleep, and biostatistics. Data inform larger NIH funded studies and, to our knowledge, provide the largest and most comprehensive, biomarker driven, characterization of brain and sex hormone levels in a racially diverse sample of middle-age women.